The invention relates to curve milling or curve grinding machines.
On machines of this kind, cam discs or cam cylinders are manufactured which have a curved surface conforming to a predetermined law. This conformity of the curve will be briefly designated as "the law of the curve". In some applications, the circumferential surface of a cam disc cylinder may describe an archimedean spiral.
Such machines have a workpiece spindle, on which the workpiece is firmly clamped and which is slowly rotated by a drive motor while the workpiece is machined by a suitable tool. The tool, such as a milling or grinding tool, is carried by a tool support, which is displaced in dependence upon the law of the curve to be machined on the rotating workpiece, while the workpiece spindle rotates about a fixed axis. The tool support is displaced relative to the axis of the workpiece spindle in dependence upon the displacement relationship predetermined by the law of the curve. Thus, each variation of the position of the workpiece due to the rotation of the workpiece spindle must be accompanied by an associated displacement of the tool support; when the desired curve in a definite region, the so called "dwell", has a constant radius, then the displacement of the tool during this period is, of course, zero.
It is known to store the mutually associated values corresponding to the angular displacement of the workpiece and to the displacement or stroke of the tool for a particular curved surface to be formed on the workpiece on a punched tape, or on a magnetic drum or other similar means and to let the angular displacement of the spindle and the linear stroke displacement of the tool take place in accordance with such stored data. This procedure is known as the so called "path control". The numerical storage values are in this case converted into analogue values to interpolate between consecutive predetermined angular dispositions of the spindle and consecutive predetermined locations of the tool support.
It is known that a single master template may be utilized to control the displacement of the tool support in a machine tool when curved surfaces are to be produced on respective workpieces which differ from each other only in scale. In such a known machine, the displacement of the master template takes place in proportion to angular displacement of the workpiece spindle in an analogue fashion and the transmission of the requisite corresponding displacement to the tool support, which displacement is determined by the shape of the master template, also takes place in an analogue fashion. The stroke scale factor is set by a linkage effective in the scanning of the master template, while the angle scale factors are embodied by different time control curves. This machine requires for each curve law only a single master template. This machine requires for each curve law only a single master template. The displacement of the master template is controlled by a time control curve having a shape dependent on the particular angular extents of the individual rise, fall and dwell sections of the cam profile to be produced by the machine. Thus, although only a single master template is required to produce each cam profile of a family of cam profiles, each having the same curve law, each different cam profile requires a different time control curve. However, a time control curve is substantially simpler to manufacture than a master template.